Calcium product



Patented July 24, 1951 2,561,862 CALCIUM PRODUCT Eugene F. Hill, Detroit, Mich assignor to Ethyl Corporation, New York, N. Y., a corporation of Delaware I No Drawing. Original application April 1, 1949, Serial No. 85,051. Divided and this application March 25, 1950, Serial No. 152,009

2 Claims. (ems-0.5)

1 This application is a division of my application, Serial No. 85,051, filed April 1, 1949, now Patent Serial No. 2,543,406. This invention relates to a new crystalline calcium product.

following which I separate the undissolved calcium metal from the resulting solution before it has had an opportunity; to react therewith in n t cea l am nt andinsuch aparticle size range. That is, more,

I In general there are two types of organic solvents reactive with an alkali metal which can be used in my process. One type forms addition products with the alkali metal and the other ,In the production of sodium by electrolysis of 5 forms substitution products therewith. Examples fused sodium chloride, calcium chloride is added of organic solvents formin addition products are to the electrolyte in order to lower its melting naphthalene, diphenyl, and anthracene. The orpoint. During the electrolysis calcium metal, as ganic solvents reactive with an alkali metal by well as sodium, is produced at the cathode, and substitution are those compounds having a hyat the temperature of operation dissolves in the drogen atom replaceable by an alkali metal. sodium melt. When this solution is removed from Compounds of this type include hydroxy hydrothe cell it is cooled and most of the calcium cryscarbons, certain amines such as methyl .amine tallizes out. This crude sodium mixture containand ethylene diamine, weak organic acids such in: the calcium metal is purified, usually by as aryl sulphonic acids and lauric acid, acetylene, mechanical separation, and most of the sodium and mercaptans such as thiophenol. recovered therefrom. The residue or sludge ob- In general the organic solvents employed in my tained from such separation consists of a mixinvention are those which react more rapidly ture of solids containing crystals of calcium with an alkali metal than 'with the calcium metal, embedded in a matrix of sodium and it also conthus permitting separation of the alkaline earth talns impurities such as sodium and calcium metal from the system before it is consumed. As oxides and chlorides. The total amount of metals mentioned above, the organic solvent should form in the residue varies but in general it is from 90 a, reaction product with the alkali metal and to 95 per cent. The amount of calcium contained should dissolve this product in order for high therein is generally between 15 and per cent. recoveries of a relatively pure alkaline earth Certain workers in this field have attempted 25 metal to be obtained. to recover some of the sodium component from For the above reasons I prefer to use as my this sludge. However, this is impractical and organic solvent hydroxy hydrocarbons, particucommercial practice has been to dispose of this larly monohydroxy hydrocarbons. Also the use sludge, by any safe means. One such means is of alcohols is preferred since the sodium alcoto return the sludge to the electrolytic cells, but 80 holates so formed can be readily recovered by this procedure is uneconomical and hazardous. removing excess alcohol. Such alcoholates are Also such residues can be disposed of by burning of considerable commercial value. Within the or by chemical means. These methods, however, term monohydroxy hydrocarbons, I include alkyl, destroy the metal components since the resulting aryl aralkyl, alkylene and cyclic alcohols having mixture of oxides and salts has no commercial only one hydroxy group. Polyhydroxy hydrocarvalue and must be wasted. None of the disposal. bons such as glycol and glycerine generally do methods are economical and all are hazardous not give as good results as the above monohydue to the danger of tfire and exrplosion Hugh: droxy hydrocarbons. When dihydroxy hydrocarsludge is contacted wi h water. rocesses a bons are used such as glycol, relatively low temhave recovered sodium have not paid for the cost 40 peratures should be employed for best results. As 01' the processing and were used primarily as a examples of monohydrox hydrocarbons, methyl, preferred means of disposal. The tcalcium value; ethyl,1propyl, isopropyl butylh and loallyl alcohol as well as the sodium values con ained in sue as wel as phenol and cresol ave een successsludges are important. Heretofore there has been fully employed in my process. noprocess for recovering the calcium values sub- M process i applicable t th separtion of stantlany free of alkali f crystalline calcium from different mixtures in An object of my mYentlon 15 to f a new which they occur with alkali metals. Referring calcium metal product in such finely divlded form specifically to the sodium-calcium sludge mixthat it is especmny Smtable for 11.58 m commerflal tures, a new form of highly reactive calcium of processes such as metal .reduct1on'.p01y t purity between to 95 per cent and higher has tions, and for the production of calcium hydride. be n re vered a um f 80 t t f I accomplish this object by treating a mixture 6 9 1 5 0 per Gen of crystalline calcium metal and an alkali metal the calcmm contamed the d with an organic solvent which reacts with the In general the crystalline calcium produced in alkali metal and dissolves the reaction product, 55 my process 15 m the form of flat platelets, the

major diameter of which varies from approximately A; of an inch to /300 of an inch or less My calcium product predominates in such a form produced by my process is obtained inLa-State of subdivision which is ideal for direct use in the abovementioned processes. Further, it can be readily converted by treatment with hydrogen to form calcium hydride which can be used-directly inmetal processes and as a drying agent, without further grinding.

The proportion of particle sizes within the above-range-can be varied in my process to suit particular needs by changing therate of coolin of the solution of calcium in alkalimetalafter-it is removed from the cell. That is, by slower cooling I can obtain a product which predominates in larger size particles or by more rapid cooling a preponderance of smaller particles may be obtained.

The temperature employed in m separation process, while not critical, is important. The operating temperature is varied according to the organic solvent employed and. the residence time of the calcium metal in the reaction medium. In general the temperature should not be-higher than the boiling point of thereaction mixture. Preferably, temperatures considerably lower than this are employed when high purit of the calcium recovered is desired. For example when a calcium-sodium mixture is treated with methyl alcohol at temperatures below 10 C.,-a high recovery of high purity calcium. is obtained. When the same mixtureis treated with ethyl or propyl alcohol somewhat higher temperatures ofthe. order of l0 C. to+l0 C. are preferably used. In general, when alcoholsareused 'asthe reaction medium the temperature should -be maintained below 100 C. In all cases, the pressure atthe temperature used should .be such as to maintain the organic solvent in theliquid' phase in order that the. alkali metal. derivativethereof will be soluble therein.

The residence time of the calciummetal. in the. reaction mixture is important. By residence time I mean the total time of contact of the alkaline earth metal with the reaction mixture. Calcium. is reactive with the organic solvents employed herein, but at a much slower rate than the alkali metal. This rate frequently does not become ap-v preciable until after the reaction between the alkali metal and the organic solvent has been completed. Thus according to my inventiomthe residence time is terminated after the time of .thereaction of the alkali metal is completed, and before noticeable amounts of calcium metals have been reacted.

The organic solvent employed also affects the average reaction rates of the metals being sepa.' rated. For example, the relative reaction rates of sodium and calcium in admixture vary'with the molecular weight of the alcohol used. The higher the molecular weight of the alcohol the less active the calcium becomes relative to the sodium: Thus ethyl alcohol is preferred over methyl"alco-- hol because of cium in ethyl alcohol ascompared' to sodium;

the low degree of-activit of cal-' In the same manner, the lower the temperature the greater the difference betwecnthe reaction ratesof the alkali metal and the calcium metal, which results in a higher recovery of the latter.

"Even under conditions in which the difference in the relative reaction rates is small, high recoveries of calcium are obtained if the calcium is removed fromthe system almost as rapidl as it is released.

When calcium in a mixture containing an alkali metal is first contacted with an organic solvent suchas ethyl alcohol substantially no reaction of the alkaline-earth metal occurs for a period of time. This time I call the induction period for the calcium. The induction period varies with the temperature employed, the organic solvent used, the typeand proportion ofmetals contained in the mixture, the impurities contained in the mixture, and the ratio ofthe organic solvent to the metallic mixture; For any given set of variables including temperature, the induction period canbe readily determined by a simple laboratory procedure as follows:

A sample ofa mixture of metals such as 'a sodium-calcium mixture is added gradually to a reaction vessel, preferably glass, containing the organic solvent and equipped with suitable temperature control and measuring means. As the metallic mixture reacts hydrogen bubbles are evolved by reaction of the sodium with the organic solvent followed by a quiescent period during which'the calcium falls to the bottom of the flask where it builds up in a layer. After a time, however, hydrogen bubbles start to appearabove this layer of calcium, and it is vigorously stirred by this evolution of gas. The elapsed time required for-the start of this vigorous evolutionof hydrogenbubbles cium on the bottom ofthe vessel is called the induction period. In this test, since initiall the only source of hydrogen bubbles is the sample of sodium-calcium it is to be noted that the bubbles allarise iromthe vicinity of the sample due to reaction of the sodium. When the induction period of the calcium is ended, the liberated calciurnstarts to react, a froth of bubbles covers theentiresurface of the reaction medium, and the calcium no longer rests quietly on the bottom of the vessel .but is dispersed throughout the reaction medium by the vigor of the gas evolution.

For example,.the inductionperiod for calcium in a sodium-calcium sludge was tested as above ina reaction medium of ethyl alcohol which had been dried over calcium hydride and subsequently distilled into a dryilask. The temperature was maintainedat l0 C. and the induction period of the'calcium was observed as over 1'75 minutes. Similarly at temperatures of 10 C. and 45 C. the-inductionperiod for calcium ina dried ethyl alcohol mediumwas 41 and 8 minutes respective- 1y. In-like-manner the induction period of calcium in a sodium-calcium sludge in methyl alcohol at '-10 C., in propyl alcohol at 45 C., and in cresol'at-45" C. was 16, 53, and over minutes respectively.

Thusfor any given temperature and reaction medium the induction period for the calcium can be determined and the maximum residence time can-be controlledso that the induction period of the calcium is not exceeded. If the alkalineearth metalis removed from the reaction mass within the induction period good recoveries are obtained.

For example the induction period for calcium in a sodium-calciumsludge when treated with anhydrous ethyl alcohol at 10 C. is 41 minutes;

from the resulting layer of cal- When such sludge was processed using anhydrous ethyl alcohol at C. with varying residence times of 34, 39 and 72 minutes, calcium was recovered in amounts of 75, 82 and 42 per cent respectively based on the calcium in the mixture. When the residence time is increased over the induction period the yields are decreased until littleif any calcium is recovered. For example, in the above type of test, when the residence time was about 6 /2 hours at a temperature of about 14 C. no calcium was recovered.

The small amount of calcium which can be recovered when it has remained in contact with dangerous to handle and otherwise unsuitable for commercial utilization. In other words an inferior calcium product is obtained. Thus I have shown the importance of residence time to the amount of recovery of the calcium. High yields of high purity calcium are obtained when the residence time is less than the induction period of the calcium but greater than the reaction time for the sodium.

One preferred mode of operation of my invention is best described in connection with separatshould be added at such a rate and in such a state of subdivision that substantially all the sodium will react with the alcohol before the induction period of the calcium which was liberated from the first portion of cludge has elapsed. By operating in this fashion the calcium will not be contaminated by pieces of unreacted sludge. The ethyl alcohol is charged to a reaction vessel provided with means of temperature measurement and with means for agitation. Suitable temperature control means, such as immersing the vessel in a constant temperature bath, are provided. Agitation is commenced and a stream of inert gas such as nitrogen may be continuously passed over the surface of the reaction medium if desired. The calcium-sodium sludge is added slowly to the vessel while maintaining the desired temperature. The reaction mass is then removed from the freed calcium and the freed calcium. is first washed with fresh quantities of ethyl alcohol, then with hexane and the hexane then removed by evaporation with an inert gas such asnitrogen.

Unless otherwise stated the parts given herein are by weight and the yield is the per cent recovery by weight of the alkaline earth metal in the mixture.

Following the above procedure, 10 parts of a mixture containing 64.5% sodium, 24.5% calcium. 2% sodium chloride and 9% sodium and calcium oxides was added gradually to a reaction vessel containing 200 parts of anhydrous ethyl alcohol. The vessel was immersed in a constant temperature bath and the temperature was maintained at 10 C. for a residence time of 90 minutes. the induction period being over 175 minutes. The reaction mass was then removed from the reaction vessel and the settled calcium re-- yield of 82% having in adding 10 parts of parts of methyl ala residence time of 15 minutes, the induction period being 16 minutes, an 83% yield of calcium having a 65.5% purity was obtained. Similarly by the use of propyl, n-butyl and allyl alcohols at temperatures of 45 C., 45 C., and 25 C. respectively, and a residence time of 14, 1020 and minutes respectively, calcium yields of 97.5, 82 and 81% respectively, having a purity of 85.3, 91 and 70% respectively, were obtained.

Likewise when mixed cresols was used as the organic solvent, and when a temperature of 45 C. for a residence time of minutes was employed, an 87.2% yield of calcium having a purity of 84% was obtained.

an 87.2% yield of calcium having a purity of 89% was obtained.

In another test conducted as above when 14.6 parts of the same metal mixture was added perature was maintained at 25 C. for a residence time of 300 minutes, a 67% yield of calpurity was obtained. In this the calcium recovery procedure was modi- At the end of the residence period the reaction mass was removed from the vessel and neutralized with cresol. The solid residue was then recovered by decantation and finally washed. The product was then dried, weighed and analyzed.

In all of the above examples the calcium prodof platelets, the major diameters of which vary between inch to inch.

2. A stable, crystalline, elemental calcium product consisting essentially of calcium platelets, the major diameter of which is less than inch.

EUGENE F. HILL.

REFERENCES CITED The following references are of record in the file of this patent:

Handbook of Nonferrous Metallurgy, Liddell, second ed., vol. 2, published by McGraw-- Hill Book Co., 1945, page 87. 

1. A STABLE, CRYSTALLINE, ELEMENTAL CALCIUM PRODUCT CONSISTING ESSENTIALLY OF AT LEAST 80% OF PLATELETS, THE MAJOR DIAMETERS OF WHICH VARY BETWEEN 1/8 INCH TO 1/300 INCH. 